I’ve been happily using SourceGear’s DiffMerge as a diff tool for years. It’s a great cross-platform tool with an ugly UI. Every now and then I check out the competition to see if there’s anything better, but I haven’t found anything that includes a similar feature set at a comparable price point. It’s hard to beat free.

Today all of that changed. DiffMerge 4 is nagware and costs $39. This isn’t necessarily a bad thing - it’s only fair that SourceGear be compensated for their work - but it means that the app loses its main advantage over the competition and gives me an excuse to shop around for a replacement.

There aren’t that many diff tools available for the Mac. Many of them can be culled immediately from the set of contenders for making basic mistakes.

Mistake #1 is using cross-platform, un-Maclike UIs. Violators are DiffMerge, Meld, P4Merge and KDiff3. Meld is the worst offender as it requires the installation of XQuartz, so I couldn’t even try that one out.

Mistake #2 is not supporting 3-way merges, which makes the tools useless with Mercurial and Git. Apple’s FileMerge is the only tool I looked at that doesn’t support this essential functionality.

Mistake #3 is a lack of new releases. If I’m going to have to invest money and time in a new diff tool I want something that is still under active development. Changes hasn’t seen any significant updates since 2009, despite being taken over by a new company. DiffFork hasn’t been updated since 2011.

Mistake #4 is stupid pricing. Most of the tools are priced at $39 or cheaper. Araxis Merge is three times that price for the cut-down version and six times for the full version.

Mistake #5, which I’m editing in at a later date, is Java. I don’t like Java for reasons far too numerous to go into here. Out goes DeltaWalker

By default, I’m left with just one choice: Kaleidoscope. I’ve mentioned it before and complained that it couldn’t “compete on price, features and speed” with DiffMerge. At $69 it’s more expensive than DiffMerge, but the difference is now between $39 and $69, rather than “free” and “not free”. Kaleidoscope offers a vastly superior UI, and having tried out many of the other options, I realise that it’s actually one of the faster diff tools out there.

It has a number of features that I immediately appreciated:

It can jump directly to each change in a file.

It shows the list of changed files in a pane of the diff window, rather than a separate window.

It shows new files in addition to changed files.

Each change is highlighted in a different colour.

It has a dark theme.

Double-clicking on a folder or file opens it in a new tab.

I’m a little annoyed that I missed out on version 2’s introductory discount price, but I downloaded it from the AppStore anyway.